Heavy crude oil from subterranean hydrocarbon reservoirs typically has four fractions: saturates (saturated hydrocarbons), aromatics, resins and asphaltene macromolecules. The high viscosity of heavy crude oil is due, at least partially, to the presence of the asphaltenes. Asphaltenes are further known to adversely impact the viscoelasticity and flow behavior of crude oil.
Asphaltenes also are known to cause operational and safety issues with both hydrocarbon production and processing. For example, they are known to have deleterious effects on the extraction of oil. For instance, asphaltenes are generally stable in bulk oil at relatively high pressures and tend to precipitate at lower pressure or onset pressure. As reservoir pressure decreases and drops below the onset pressure during hydrocarbon production, asphaltenes precipitate and the precipitates block production routes and tubing.
Asphaltene precipitates are further known to flocculate and form deposits in the pores of the formation, coat boreholes and solidify in downhole equipment. Wells with excessive asphaltene deposition may incur high remediation costs but, more importantly, are exposed to levels of formation damage that can greatly shorten the productive life of the well.
In the past, much effort has been undertaken in order to decrease the viscosity of heavy oil and to increase the flow of hydrocarbons from the well by minimizing the precipitation of asphaltenes. Such efforts have been focused on determining an effective catalyst for breaking the bonds of the asphaltenes. However, catalyst selection has not been totally effective. This is attributable, in part, to the fact that catalyst selection has only been based on the activity, selectivity, ease of regeneration and mechanical strength of the catalyst under defined cracking operations.
Improved methods for decreasing the viscosity of heavy oil and to break down asphaltenes are therefore desired.
It should be understood that the above-described discussion is provided for illustrative purposes only and is not intended to limit the scope or subject matter of the appended claims or those of any related patent application or patent. Thus, none of the appended claims or claims of any related application or patent should be limited by the above discussion or construed to address, include or exclude each or any of the above-cited features or disadvantages merely because of the mention thereof herein.